Electrical signaling system and signaling method



May 7, 1929- A. N. GOLDSMITH ET AL 1,712,036

ELECTRICAL SIGNALING SYSTEM AND SIGNALING METHOD Filed Nov. 20, 1924 2 Sheets-Sheet l @IML m .Sk

INVENTOR R D N. GULDSMITH H R WWK ATTORNEY May 7, 1929. A. N. GoLDsMl-rH ET AL 1,712,036

ELECTRICAL SIGNALING SYSTEM AND SIGNALING METHOD Jil @Mmmm Q' v t? BY THU EVA oYcK hun Mm TORNEY of the desired beat frequencies.

Patented May 7, 1929. l

UNITED STATES 1,712,036 PATENT OFFICE.

ALFRED N. eoLDsMrrH, or NEW Yonx, AND An'rnua E. VAN DYcx, or EYE, 'NEW Yoan, AssIeNoas 'ro EADro common-Anon or AMEEICA, A conroEATIoN or DELAWARE. l

ELECTRICAL SIGNALING SYSTEM AND SIGNALING METHOD.

Application led November 20, 1924. Serial No. 751,031. v

Our invention relates to electrical systems and particularly tov electrical signaling systems for the reception and detectin of signal waves by utilizing the principle o so-called beats.

Heretofore in electrical signaling systems employing beat frequencies obtained by generating and combining suitable auxiliar frequencies with the signal Waves certain disadvantages resulted Which are as follows:

With the reception of desired signal Waves of a given frequency a plurality of adjustments of the device supplying the `auxiliary frequencies was possible for the production This naturally resulted in confusion to the operator of the system.

Also one particular adjustment of the device supplying the auxiliary frequencies resulted in the production of the desired beat frequency not only from the desired signal Waves but from certain undesired Waves as Well. This resulted in interference.

One of the principal objects of our invention is the provision of systems utilizing the beat frequency principle in which substantially only one adjustment of the device for c generating the auxiliary frequency is .pos-

sible for the production of the desired beat frequency from the signal Waves.

Another principal object of our invention is the provision of a system utilizing the beat frequency principle in which With a certain adjustment of the device for generating the auxiliary frequency, the desired beat freuency is produced only from the desired signal Waves and not from certain undesired signal Waves.

Another obj ect of ourfinvention is the simplification of the controls in such systems.

Other objects and advantages inherent in our invention will be apparent from the following description taken in connection with the accompanying drawings, in which:

Fig. 1 is a schematic diagram of a simple heterodyne system,

Fig. 2 is a schematic diagram'o'f a simple autodyne system and Fig. a schematic diagram of a combined autodyne' and reflexing system.

Referring to Fig. 1, an antenna 1 is connected to ground Gr` through the primary winding of the coupling de vice 2, the sec- Plldfy Wllng 0f Whlcll 1S connected to the input terminals of an electrical filter A. A'varlable condenser 3 is connected in shunt with the secondary winding for properly tuning the antenna circuit to the incoming slgnal Waves. The electrical filter A is of the low pass type and comprises av plurality of reactance coils 4 connected in series and a. plurality of variable condensers 5 connected 1n shunt as shown.

yThe output terminals of the filter A are connected to the input terminals of a detector device as shown.

The local oscillation generator is inductively coupled to one of the output leads of the filter A as shown. The output terminals of the detector device may be connected to the sound reproductive device 6 through a plurality of audio frequency amplifiers as shown.

Referring to Fig. 2 an antenna 10 is connected to ground G through the primar winding of a coupling device 11, the secon ary Winding of which is connected to the input terminals of electrical filter B. A variable condenser 12 is connected in shunt with the secondary winding for properly tuning the antenna circuit to the incoming'signal waves.

The filter B is of the loW pass type and comprises a plurality of reactance coils connected in series and a plurality of variable condensers 14 connected in shunt as shown.

The output terminals of filter B are inductively coupled tothe combined detector and oscillation generator by means of the coupling device 15. The output terminals of the detector and oscillation generator may be connected to the sound reproductive device 16 through a plurality of audio frequency amplifiers as shown.

Referring to Fig. 3 an antenna 2O is connected to ground G through the primary winding of inductive coupling deviceQl, the secondary Winding of which is connected to the input terminals of an electrical filter C. A variable condenser 22 is shunted across the secondary Winding for properly tuning the antennacircuit to the incoming signal waves.

The filter C, which is of the loW pass type, comprises a plurality of reactance coils 23 connected in series and a plurality of variable condensers Q4 connected in shunt as shown. The outputterminals of the filter C are @0nnected `across the grid filament of 3element tube 25 which serves as a radio frequency amplifier.

The plate of tube 25 is connected to the grid of the combined oscillating and detecting tube 26 through a small blocking condenser 27 for preventing the impression of the B battery voltage of the plate filament circuit of tube 25 on the grid element of the tube 26.

An inductance coil 27 is connected across the grid and filament of tube 26, a variable tuning condenser 28 being connected in shunt with the said coil. The plate filament circuit of tube 26 comprises the plate battery B1, primary winding of beat frequency transformer 29 and a tickler coil 30 inductively coupled to the inductance coil 27, the battery B1 with primary winding of beat frequency transformer 29 and the tickler coil 30 all being connected in series.

A condenser 31 is shunted across the primary winding of transformer 29 for bypassing the high frequency oscillations and for tuning the transformer to the desired beat frequency and a blocking condenser 32 is so connected in one of the leads connecting one of the output terminals of the filter C to the grid of tube 25 as to prevent the intermediate frequency oscillations being impressed on the antenna and'at the same time so connected as to be excluded fromthe antenna and filter circuits.

The secondary winding of beat frequency transformer 29 is connected across the gridfilament of tube 25, the connection to the grid of tube 25 being made between the grid and the condenser 32. The plate-filament circuit of tube 25 also comprises the primary Winding of beat frequency transformer 33 and a B-battery both connected in series, the connection to the plate of tube 25 not including the condenser 27. The secondary Winding of beat frequency transformer 33 is connected across the input terminals of the beat frequency amplifier. n v

The output terminals of the beat frequency amplifier are connected to the input terminals of the detector device as shown. The output terminals of the detecto-r device may be connected to a sound reproductive device 35 through a plurality of audio frequency amplifiers as shown.

The filaments of the various tubes may be supplied with heating current from a shitable source of power A1 and the currents in the individual filaments may be independently controlled by the various rheostats R.

In each of the systems shown by Figs. 1, 2 and 3 of the drawing, the antenna tuning condenser, the filter condensers and the oseillation generator are all preferably simultaneously controlled by a single control device as shown, thereby eliminating the disadvantage of multiplicity of controls. However, we

do not limit ourselves to this sinvle control arrangement, but may control the various variable elements in our systems separately or in various combinations.

Therefore, according to our preferred arrangement when the single control device is moved to a predetermined position the antenna circuit is tuned to signal waves of a certain frequency the cut-off point of the electrical filter is simultaneously adjusted to prevent the passage of interfering waves and the oscillation generator is also simultaneously adjusted to generate an auxiliary frequency of the proper value to combine with the desired signal waves.

While We have shown and described low pass filters incorporated in our various systems we do not limit ourselves to filters of this type, but may employ high pass filters, band filters or various combinations of these filters depending on the auxiliary frequency as compared with the frequency of the desired signal waves.

As the systems shown in Figs. 1 and 2 func-v tion in substantially the same manner, the only difference being that one is of the heterodyne type while the other is of the autodyne type, a single description of the operation of both systems is thought to suffice.

Assume that the signal waves to be detected possess afrequency of 600 kilocycles. \The single control element is moved to a predetermined position which simultaneously tunes the antenna circuit to the 600 kilocycle signal Waves, the oscillation generator circuit to cause the generator to produce an auxiliary frequency of say 610 kilocycles and the electrical filter to prevent the passage of waves having a greater frequency than a value slightly above the frequency of their signal `waves, 600 kilocyeles in this concrete example. The 600 kilocycle signal waves and the 610 kiloeyele auxiliary combine to produce 10 kilocycle beats, which are detected and amplified. It is thus apparent that the desired beat frequency waves are only obtainable from signal waves of a certain frequency when the single control device oceuples one predetermined position rather than a plurality of positions when a separate control device is employed for the oscillation generator.

Assume now that undesired Waves of a frequency of 'say 620 lkilocycles impinge on the antenna. In systems heretofore used the antenna circuit could nbt be tuned sharply enough to prevent its `being influenced by these undesired Waves. These Waves would, of course, combine with the 610 kilocycle auxiliary Waves to produce the 10 kilocycle beat waves. Interference was the result. In our systems the electrical filter, having a cutoff point at a frequency slightly above the desired frequency, (600 kilocycles isthe concrete example given) will prevent passage of these undesired Waves and consequently they Waves (600 kilocycles). Undesired Waves of say 580 kilocycles would then be prevented from combining with the auxiliary Waves of 590 kilocycles to produce the desired l0 kilocycle beat frequency Waves. Interference .would be similarly prevented in this case also.

The system shown in F ig.3 functions as follows:

The single control device is moved to a predetermined position which simultaneously operates, first: the condenser 22 to tune the antenna circuit to the frequency 0f the desired signal waves, second: the condenser 28 to properly tune the plate circuit of the oscillation generator 26 to cause it to generate auxiliary waves at a frequency equal to the frequency of the signal waves plus the frequency-of the desired beat frequency Waves and third: the condensers 24 of the low pass filter C to properly tune the low pass filter C to prevent the passage of Waves having a frequency greater than the frequency of the desired Waves.

The incoming signal Waves are impressed on the id filament of the radio frequency amplifying tube 25 Where they are amplified. These oscillations are then impressed on the grid of the combined oscillating and detecting tube 26. By meansrof the tickler coil 30 and the proper adjustment of the variable condenser 28, as described above, the tube 26 is made to produce auxiliary waves of a frequency equal to the frequency ofthe incoming signal waves plus the desired beat plate-filament circuit of tube 26 are now impressed on the grid and filament of tube 25 y means of the beat frequency transformer 29, the condenser 31 by-passing al1 the high frequency oscillations and also serving to tune the plate filament `circuit of tube 26 to the desired beat frequency Waves. The beat frequency waves, considerably amplified by tube 25, will now appear in the plate filament circuit of tube 25, in which is included the primary winding` of beat frequency transformer 33, the secondary Winding of wlnch 1s connected to the input terminals of the beat frequency amplifier-as shown.

'lhe output terminals of the beat frequency amplifier are connected to the input side of the detector in which the beat frequency oscillations are detected. The audio frequency oscillations appearing in the output side of the detector are now impressed on the sound reproductive device 35 through a plurality of audio frequency amplifiers as shown.

As explained above in connect-ion with the svstems shown by Figs. l and 2, the electrical -filter C, may be of the high pass type, low

pass type, the band type, or a combination of these various types of filters depending on the desired relationship of the frequency of the auxiliary Waves to the frequency of the signal waves to be detected.

While We have shown and described various modifications of our invention We do not limit ourselves to said modifications, but may employ such other embodiments as may come within the spirit and scope of our invention.

Having described our invention, what We claim is:

1. The combination of an input circuit responsive to Waves, adjusting means for tuning said circuit, electrcal filter means cooperating with said input circuit and permitting only the passage of desired signal Waves of certain predetermined frequencies, adjusting means for tuning said filter, means for producing beat frequency Waves from the desired signal Waves, adju-sting means for said beat producer and a single control device for simultaneously actuating the said adjusting means of said input circuit, said filter means and said beat frequency producing means.

2. The combination of an input circuit responsive to Waves, adjusting means for tuning said circuit, electrical filter means cooperating with said input circuit, adjusting means for tuning said filter circuit, means for producing oscillations, adjusting means for controlling the frequency of said oscillations and a single control device for simultaneously actuating the said adjusting means, said input adjusting means and said oscillator adjusting n'ieans being cooperatively arranged to give a constant super-audible local frequency and said input, oscillator and filter circuits beingarranged to be cooperatively tuned by said control member to cause the input and filter to admit a desired frequency and to cause said filter to exclude an undesired frequency which differs from the oscillator frequency by substantially the same amount as the oscillator differs from the desired signal.

3. In a super-heterodyne receiver, the combination of a vaiiably tuned input circuit, a variably tuned oscillator circuit for generating a beat frequency,a tuned intermediate frequency circuit for amplifying the beat frequency and a timed filter circuit, said last mentioned circuit being adapted to filters cuit.

4. In a super-heterodyne receiver, the combination of an input circuit, a variable condenser for tuning said circuitto the frequency being received, an oscillator circuit for generating the beat frequency, a variable condenser for varying the frequency of the oscillator circuit, an intermediate frequency circuit for amplifying the beat frequency and a filter circuit including a plurality of condensers for varying the frequency, which the said filter circuit isadapted-to filter and prevent an undesired frequency being passed which would, in combination with the oscillator frequency, produce a beat frequency ampliiiable by said intermediate frequency circuit. Y

5. In a super-heterodyne receiver, the combination of an input circuit, a variable condenser for tuning said circuit to the frequency being received, an oscillator circuitI foi` generating a beat frequency, a variable condenser for varying the frequency of the oscillator circuit, a tuned intermediate frequency c1rcuit,fa filter circuit comprising a plurality of condensers for varying the frequency which the said filter circuit is adapted to filter and prevent undesirable signals being passed, which would, in combination with the oscillator frequency, produce abeat amplifiable by said intermediate circuit and a single control device for simultaneously vvarying all of said condensei's and therefore the frequency to which the receiver is set to receive.

6. In a heterodyne radio receiving apparatus, a combination of an input circuit, a variable condenser for tuning said circuit, a vacuum tube oscillator for generating beat frequency,a variable condenser for determining the frequency of said oscillator, a filter circuit between said input circuit and said oscillator, a variable condenser for determining tlie tuning of said filter circuit and a single control device for simultaneously varying all of said condensers, the capacity of said input and filter condensers being adjustable by said control member for maintaining like tuning throughout their range, wherebyI beats from undesirable signals are prevented and re-radiation of beat frequency is prevented and said oscillator condenser being controlled throughout its range by said controlling member to tune said oscillator to a constant difference frequency with respect to the tune of the input and filter circuits.

7. The method of preventing signal interference in a superheterodyne set comprising an input circuit, an oscillator circuit and a selective absorption circuit, by a second materially different frequency which would heterodyne with the oscillator frequency to give the same beat frequency as that between the desired signal frequency and the oscilliator frequency which consists in tuning the input to the desired frequency and simultaneously tuning the absorption circuit in such electrical relation to said input circuit that said second frequency is removed.

S. In a radio receiving system the combination of means responsive to desired signal waves, adjustable means for producing auxiliary waves adapted to combine with said desired waves to reduce a beat frequency, adjustable means or permitting only the passage of desired signal waves of certain predetermined frequencies and a single control device for simultaneously tuning each of the last-mentioned adjustable means.

9. A radio receiving system comprising means for tuning its input, adjustable means for reducing 'a desired signal frequency simultaneously with a materially different interfering frequency to the same lower fre uency, variable means for removing the un esired frequency and means common to the three above mentioned means for varying them simultaneously.

10. In a radio receiving set utilizing the beat note method of signal reception, employing an input circuit, an oscillator circuit and a frequency selective impedance associated with the inputcircuit, the method of ,reducing interference which consists in tuning the frequency selective impedance and the input circuit to different frequencies, each of these frequencies differing from that of theoscillator circuit by the same amount, and maintaining the abovestated frequency relation of the two circuitsand the frequency selective impedance throughout the range of the set.

11. A signal responsive system comprising an input circuit including tuning means, an oscillator circuit including tuning means, a filter circuit including timing means, means for mechanically coupling said tuning means for simultaneous adjustment to maintain con stant the difference of the input and oscillator circuit frequencies and to maintain the filter circuit so tuned as to filter outa-n undesired freqluency which differs from the frequency of tie oscillator circuit by an amount equal to half` the difference between said undesired frequency and the frequency of said input circuit.

12. In a signal responsive system comprising an input circuit with tuning means, an oscillator circuit including vtuning means, an absorption circuit including tuning means and an intermediate frequency amplifier, the method of eliminating interference which consists in tuning the input circuit to the desired signal frequency, tuning the oscillator circuit for a frequency differing from that of the input circuit by the frequency for Which the intermediate frequency amplifier is designed, tuning the absorption circuit for a frequency different from that of the input circuit, and differing from that of the oscillator circuit by the frequency of the intermediate frequency amplifier, and maintaining the above stated frequency relation of the three circuits throughout the range of the system.

13. A signal responsive system comprising an input circuit including tuning means, a filter circuit having a plurality of variable reactances, and means simultaneously to vary said tuning means and said reactances, Whereby to maintain a predetermined relationship between the frequency to which said input circuit is tuned and the frequencies to which said filter circuit is responsive.

14. A signal responsive system comprising an input circuit including tuning means, a filter circuit having a plurality of variable reactances connected to said input circuit, said filter being designed to pass only a predetermined range of electrical frequencies, and means simultaneously to vary said first mentioned tuning means and the Variable reactances.

15. A radio receiver comprising in combination, an input circuit, variable means to tune said input circuit, an absorption circuit connected t0 said input circuit, said absorption circuit comprising a plurality of variable reactances, a local oscillation generator, means variably to tune said oscillation generator, and single means simultaneously to Vary both said tuning means and. said variable reactances.

1.6. In a radio receiver having an input circuit, means to tune said input circuit, a filter connectedto said input circuit, said filter having a variable tuning means, a local oscillation generator coupled to said filter, means to tune said local oscillation generator, and single means to vary all of said tuning means.

1?. In a radio receiver utilizing the beat note method of signal reception, a tuned anreactances, whereby to maintain said predetermined frequency differences for various settings of the said first mentioned tuning means.

ALFRED N. GOLDSMITH. ARTHUR F. VAN DYOK. 

